Mold material mixture containing additives for reducing casting defects

Abstract

The subject matter of the invention is mold material mixtures for producing molds or cores for metal casting, consisting of at least one refractory base mold material, a binder and an additive based on factice. The invention also relates to a component system, a method for producing molds and cores using the mold material mixtures or the component system respectively, and to molds and cores produced by said method.

Description

[0001]The invention relates to mold material mixtures for producing molds or cores for metal casting, consisting of at least one refractory base mold material, a binder and an additive based on factice. The invention also relates to a component system comprised of refractory mold base material, binder and factice, to a method for producing molds and cores using the mold material mixtures or the component system respectively, and to molds and cores produced by said method.BACKGROUND OF THE INVENTION[0002]Casting molds are essentially comprised of molds or molds and cores which represent the negative form of the cast piece to be produced. The molds and cores here generally consist of a refractory mold base material, such as quartz sand, and a suitable binder which provides the cast mold with sufficient mechanical strength after removal from the mold tool. The refractory mold base material is preferably present in free-flowing form, so that after mixing with the binder it can be poured...

AI Technical Summary

Benefits of technology

The patent text explains that using factice in the mold material mixture can reduce the tendency of veining in the casting of iron and steel. Additionally, using factice can reduce the tendency of adhesion on the mold tool, which reduces the frequency of cleaning and costs.

Problems solved by technology

These changes of volume are responsible for mechanical stresses in the microstructure of the sand near to the boundary surface between the molten metal and sand, which can lead to cracks in the molds / cores, which enable the penetration of molten metal into the molds / cores and thus veins arise at the surface of the casting.

Veins are irregular, filigree, thin metallic protrusions which are difficult to remove, particularly in angles or on corners and edges of the cast pieces.

These veins are undesirable and must be removed with great time and effort, associated with increased costs.

Veins are difficult to detect at these places and often cannot be removed.

However, they are also significantly more expensive.

This thin layer of carbon makes it more difficult for the molten metal to wet the sand grains and inhibits penetration of the liquid metal into the sand microstructure.

Despite the great number of possible additives, the difficulty of “veins” is not resolved for all application scenarios.

This frequently adversely affects other important properties, such as the strengths of the molds and cores or the processing time of the mold material mixtures.

Sometimes other casting defects also occur.

The use of additives can also lead to undesired contamination in the tool, for example by red ferric oxide.

Such contamination then frequently leads to an increased tendency of adhesion and makes more frequent cleaning of the core box necessary.

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